/*
Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.

An example is the root-to-leaf path 1->2->3 which represents the number 123.

Find the total sum of all root-to-leaf numbers.

For example,

    1
   / \
  2   3
The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.

Return the sum = 12 + 13 = 25.
*/

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    void sumHelper(TreeNode *node, int cur, int &sum) {
        cur = cur * 10;
        if (node->left == NULL && node->right == NULL) {
            sum += (cur + node->val);
            return;
        }
        if (node->left) sumHelper(node->left, cur + node->val, sum);
        if (node->right) sumHelper(node->right, cur + node->val, sum);
        return;
    }
    int sumNumbers(TreeNode *root) {
        if (!root) return 0;
        int sum = 0;
        sumHelper(root, 0, sum);
        return sum;
    }
};

